Here this explains it in crayons, my favorite media 
http://parallaxscurioandrelicfirearmsforums.yuku.com/topic/3361/t/Headspace-101-for-303-s.html
http://parallaxscurioandrelicfirearmsforums.yuku.com/topic/3361/t/Headspace-101-for-303-s.html
Headspace & Head Clearance - Not The Same According To SAAMI
- Thread starter Bullet
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USSR
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Idano,
That link deals with rimmed cartridges which headspace on the rim. Totally different animal from the rimless cartridges commonly used today, hence I stated in my post:
Don
That link deals with rimmed cartridges which headspace on the rim. Totally different animal from the rimless cartridges commonly used today, hence I stated in my post:
Magnum cartridges such as the 7mm Magnum also headspace differently.
Don
Owen
Moderator Emeritus
i wish I could find my SAAMI/CIP books on CD/R
I knew if I was tenacious enough I would find the article that would spell it out for all of us literary challenged folk who rely on picture books for our education. See if this article doesn't clearly define headspace versus head clearance.
http://www.switchbarrel.com/Head.htm
I had always knew about headspace but never heard of head clearance until this thread and the above article; you learn something new everyday.
Just my $0.02 but if there is still an argument after reading the above article you either just like to argue or ....
http://www.switchbarrel.com/Head.htm
I had always knew about headspace but never heard of head clearance until this thread and the above article; you learn something new everyday.
Just my $0.02 but if there is still an argument after reading the above article you either just like to argue or ....
dmftoy1
Member
So if I'm reading those articles correctly . . . .
A .303 Go and a .303 "field" gauge are attempting to ensure that you don't have excessive "head clearance".
Am I missing something? (I know it's a rimmed cartridge . ..just trying to test my understanding of what I've read)
A .303 Go and a .303 "field" gauge are attempting to ensure that you don't have excessive "head clearance".
Am I missing something? (I know it's a rimmed cartridge . ..just trying to test my understanding of what I've read)
scrat
Member
omg guys give it a rest before this thread gets locked too
Owen
Moderator Emeritus
no reason to lock this thread as long as its civil.
What Bullet can not seem to get over is the fact that head clearance is a moot point. Who cares. Headspace includes it and is the only important one of the two. Originally the thread was about being careful not to create excessive headspace by pushing the shoulder back too far. That is the point. Bullet keeps pounding us about this meaningless head clearance deal, when the excessive headspace is the danger. We do not say there is no such thing, we say it is meaningless because headspace includes it.
Interesting article, by the way, but does not sway me.
Interesting article, by the way, but does not sway me.
Agreed.
Walkalong,
I agree with you that head clearance is a moot point in regards to reloading; it's a gun building specification an one of those nice to know but not really all that germane to general reloading. In 30 years of reloading I have never had to know anything about head clearance, however, I did have to learn about head space when I bought a new .222 Model 70 back in 1978 that had the head space set too short; only 4 out of the the first box of 20 brand new Winchester ammo chambered the first day out. Other then that one incident I have never had an issue with head space: tight or excessive.
I agree with you that head clearance is a moot point in regards to reloading; it's a gun building specification an one of those nice to know but not really all that germane to general reloading. In 30 years of reloading I have never had to know anything about head clearance, however, I did have to learn about head space when I bought a new .222 Model 70 back in 1978 that had the head space set too short; only 4 out of the the first box of 20 brand new Winchester ammo chambered the first day out. Other then that one incident I have never had an issue with head space: tight or excessive.
Owen
Moderator Emeritus
Walkalong,
Bullet's point is that its possible to have excess Head Clearance on a rifle with perfectly fine headspace.
Headspace is a characteristic of the rifle alone. What we are concerned with is the fore-and-aft slop between the chamber and the cartridge. That would be head clearance. Head clearnace is controlled by two things: the headspace dimension of the rifle, and the length of the cartridge at the reference dimension.
Saying a single dimension defines a clearance is off the mark. if that was the case, we'd only need one size drill, and any old bolt would fit through the hole perfectly.
Unless, of course, the cartridge was really FUBAR. Then we call it fire forming.
Bullet's point is that its possible to have excess Head Clearance on a rifle with perfectly fine headspace.
Headspace is a characteristic of the rifle alone. What we are concerned with is the fore-and-aft slop between the chamber and the cartridge. That would be head clearance. Head clearnace is controlled by two things: the headspace dimension of the rifle, and the length of the cartridge at the reference dimension.
Saying a single dimension defines a clearance is off the mark. if that was the case, we'd only need one size drill, and any old bolt would fit through the hole perfectly.
Unless, of course, the cartridge was really FUBAR. Then we call it fire forming.
Owen
Moderator Emeritus
idano, the problem you had was insufficient clearance, aka an interference fit. In this case the rifle was the problem. If the cartridges were too long, the symptom would have been identical; you would have been unable to close the bolt.
If the cartridges are too short, or the headspace is too long the symptoms tend to be case separation and light strikes.
If the cartridges are too short, or the headspace is too long the symptoms tend to be case separation and light strikes.
owen, If I may reply.
Idano
In your link I believe they are talking about when you change barrels or install barrels you need to get the correct clearance between the bolt face and the chamber walls. If there is too much clearance between the bolt face and the chamber walls either there is a problem with the bolt or the chamber is not correct (rifle problem). Not the same as what SAAMI’s head clearance is talking about from the bolt face to the case head. I believe this is part of the problem with head clearance and headspace as listed by SAAMI, because many sources don’t seem to go by SAAMI’s definitions which makes it more confusing.
I believe your first link accurately depicts what SAAMI is referring to but with a rimmed case.
In your first link the only way a reloader could change the head clearance would be by not resizing your case enough to where it would headspace from the shoulder. Depending on how much you resized the case it could have 0 head clearance. Sizing the case (smaller) would not effect head clearance.
In a case that normally headspaces from the shoulder the more you resize the case (smaller) the more head clearance you create and a reloader that only neck sizes would have 0 head clearance.
.
Idano
In your link I believe they are talking about when you change barrels or install barrels you need to get the correct clearance between the bolt face and the chamber walls. If there is too much clearance between the bolt face and the chamber walls either there is a problem with the bolt or the chamber is not correct (rifle problem). Not the same as what SAAMI’s head clearance is talking about from the bolt face to the case head. I believe this is part of the problem with head clearance and headspace as listed by SAAMI, because many sources don’t seem to go by SAAMI’s definitions which makes it more confusing.
I believe your first link accurately depicts what SAAMI is referring to but with a rimmed case.
In your first link the only way a reloader could change the head clearance would be by not resizing your case enough to where it would headspace from the shoulder. Depending on how much you resized the case it could have 0 head clearance. Sizing the case (smaller) would not effect head clearance.
In a case that normally headspaces from the shoulder the more you resize the case (smaller) the more head clearance you create and a reloader that only neck sizes would have 0 head clearance.
.
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That is covered in the headspace issue. My point is "head clearance" is meaningless. Take care of headspace and everything will be fine. Headspace takes all clearance into consideration. That is why headspace is important and everyone talks about it. No one talks about head clearance, because it is meaningless. It is just along for the ride with headspace.
Wrong. It is a combination of chamber and cartridge.
Ludicrous.
And you almost got it the other day Owen.
Well this has been an educational thread to say the least. If it hadn't have been for the hub bub I wouldn't have learned what head clearance was so I thank you all but I am done responding.
http://www.switchbarrel.com/Head.htm
http://www.switchbarrel.com/Head.htm
Idano said:
Sunray
Sunray
I believe you are a wise man, A Word to the Wise is Sufficient. Thank you for your posts. Without them I wouldn’t have realized the difference between head clearance and headspace and in future threads I’ll try to follow your example more.
Sunray
I believe you are a wise man, A Word to the Wise is Sufficient. Thank you for your posts. Without them I wouldn’t have realized the difference between head clearance and headspace and in future threads I’ll try to follow your example more.
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